Sifting off track ballast

In 2019, we received a cool challenge from the company Sersa Group from Switzerland. They were looking for a screening machine that had to meet the following conditions:

Maximum width = 150cm.
Sifting in 3 fractions (0 - 30mm / 30 - 60mm / +60mm) where with the 0-30 and the +60mm fell on the front of the machine and the 30-60mm (clean ballast) on the other side of the machine.
The machine is on a mountain slope so the material must be able to slide off the machine both uphill and downhill.
It should be on a carriage so that it can be pulled along by an excavator crane.
Sifting nets strong enough to sift out railroad ballast.
Our design consisted of 2 Mini Screeners placed one above the other with a conveyor belt at the bottom. The conveyor discharges the 0-30mm fraction to the front of the machine where it converges with the +60mm fraction. On each machine, the slope can also be adjusted individually by means of a hydraulic jack located under the screener. Instead of using screening nets, punch plates were chosen in this case.